Leaf Litter Breakdown and Soil Microbes in Catalpa bungei Plantations in Response to Various Fertilization Regimes

Litter decomposition propels the geochemical cycle by returning nutrients to soil. Soil microbial communities play an important role during litter breakdown wherein various fertilization regimes are conducted. In this study, we carried out a five-year fertilization experiment in a young Catalpa bungei plantation in northern China. The fertilization strategies employed mainly included the integration of water and fertilizer (WF), hole fertilization (HF), and no fertilization (CK) as a control. We tracked the decomposition dynamics of leaf litter and identified the major microbial communities involved in litter breakdown for each fertilization regime. The results showed that fertilization increased the biomass and C content of leaf litter, and the C storage in the HF forest was higher than that in the WF forest. Fertilization significantly decreased leaf litter decomposition and nutrient release and prolonged the duration of breakdown. The breakdown of litter in the WF stand was slower than that in the HF stand, but the diversities of bacteria and fungi were higher in the WF soil. The community structures of bacteria and fungi in the WF soil showed obvious differences compared to those in the CK and HF soils. Fertilization strengthened competitive relationships but decreased cooperative interaction among microbes. The abundances of saprophytic fungi and decomposing bacteria in the WF soil were lower than those in the HF soil. The key flora, including Arthrobacter and Neocosmospora, regulated litter breakdown in the HF and WF forests. In addition, Arthrobacter, Filobasidium, and Coprinopsis were mainly involved in the decomposition process in the nonfertilized forests. Thus, studying the biomass and initial quality of litter treated with different fertilization measures and exploring the characteristics of nutrient release during litter decomposition are both of significant value with regard to deepening understanding of the effects of different fertilization methods on litter breakdown and their associated response mechanisms.